Digital I/O timing can be controlled by one of the following methods:

•Onboard clock on 653X (DIO-32HS) devices

•User-supplied clock

•Change detection mode (input only), where a pattern is acquired whenever there is a state transition on one of the data lines

There are two general categories of timed digital I/O:

•With Finite Timed Digital I/O, a predetermined number of patterns are acquired or generated at a rate controlled by one of the timing sources discussed above.

•With Continuous Timed Digital I/O, digital data is continuously acquired or generated until the user stops the process. The rate can be controlled by one of the timing sources discussed above.

Finite Pattern I/O

In finite pattern I/O mode, LabVIEW allocates a single buffer of computer memory large enough to hold all the patterns. Optionally, you can use triggering in this mode of digital I/O.

Finite Pattern I/O without Triggering

In this mode, the start and/or stop of the digital I/O process is not controlled by an external trigger event. Instead, it initiates as soon as the VI is run.

The Buffered Pattern Input VI and Buffered Pattern Output VI show how to perform finite pattern I/O. In these examples, the 653X onboard clock is programmed to the clock frequency value when the clock source parameter on the VI front panel is set to internal. A user-supplied clock is used when the clock source is set to external. Refer to the VIs in examples\daq\digio.llb for examples of how to perform finite pattern I/O.

The Change Detection Input VI reads in a fixed number of patterns, where each pattern is read in when there is a state transition on one of the data lines. Further, the line mask parameter can be used to selectively monitor transitions only on certain lines. Refer to the VIs in the examples\daq\ digio.llb for examples of how to read in a fixed number of patterns.

The Multi Board Synchronization VI shows how to synchronize two 653X devices to acquire data simultaneously. Refer to the VIs in the examples\daq\digio.llb for examples of how to synchronize two 6533 devices.